Citroen C4 1.6 VTi running rich and stumbling

[Off_Da_Wall]

Before I start I'm aware it's a Citroen and has the dreaded Prince engine but I'm stubborn and won't let it get the better of me.

So the car isn't running right suffering from the following symptoms: rich exhaust fumes, stuttering at low rpm(setting off and crawling is a pain), rev hanging around 2k rpm. The car seems to slightly improving as it warms up but still isn't right. If I get it up to a higher rpm in 1st and then shift then the rev hang isn't so apparent. The car has no EML present, but I have had it give me a P0420 code on longer drives. In terms of repairs, the vehicle has had quite a lot done to it just to get it to where it is now. Originally the car suffered from a constant knock sensor fault (ended up being a faulty ecu) and its original engine skipping a tooth on timing. The local mechanic did the timing chain and the engine would not run when timed correctly(The mechanic gave in and found a replacement engine to which he did the timing chain and the car would run.) The replacement engine was taken from a running car said to have no engine issues.

I'm at a loss as to what the problem could be but my thoughts are to check -

Camshaft vanos timing solenoids on both inlet/exhaust
Readings on the pre and post O2 sensors
Condition of the catalytic converter - is it blocked?
Consider carbon cleaning service

My question is has anyone had a vehicle suffer similar symptoms and how am I best troubleshooting them?

[E-bmw]

What year is it?

Check for un-metered air leaks which would cause the ECU to enrichen the mixture.

Most common in the intake pipework/rubbers from air filter to engine.

I assume you mean the 1.6 Turbocharged engine?

Decoke is commonly a possible helpful factor.

[Off_Da_Wall]

E-bmw said:

What year is it?

Check for un-metered air leaks which would cause the ECU to enrichen the mixture.

Most common in the intake pipework/rubbers from air filter to engine.

I assume you mean the 1.6 Turbocharged engine?

Decoke is commonly a possible helpful factor.

It's a 2010 and I was looking to possibly simplify the intake system because it's a stupid setup. It's the NA version so a little simpler I guess. The car uses a MAP sensor so only an inlet manifold leak would have an effect right?

[Flyingferret]

Coolant temperature sensor - my mum had a c3 with the 1.6 and it ran like a pig, wouldn’t idle or run very well. No fault code present for it either. It was defaulting to warm running settings and the ECU was throwing a fit. Cheap and handy to see if it fixes the fault.

[Megaflow]

It might not have an engine management light on, but does it have any fault codes? That is the first question.

I’d also be very sceptical about a constant knock sensor issues being a faulty ECU. ECU’s are generally very reliable, they have no moving parts and live inside the car or a waterproof enclosure. The sensors and wiring that feed them not so much.

Did the original engine get the knock sensor problem fixed before the timing chain jumped a tooth or during?

[Off_Da_Wall]

Megaflow said:

It might not have an engine management light on, but does it have any fault codes? That is the first question.

I’d also be very sceptical about a constant knock sensor issues being a faulty ECU. ECU’s are generally very reliable, they have no moving parts and live inside the car or a waterproof enclosure. The sensors and wiring that feed them not so much.

Did the original engine get the knock sensor problem fixed before the timing chain jumped a tooth or during?

Shows no active codes and I can only get a P0420 when I take it on a long journey. The car had a knock sensor fault when I first bought the car thinking it was an easy fix replaced the sensor, checked the sensor connector, checked the ecu connector and checked the continuity from ecu connector to the sensor connector. The original engine would not run when timed correctly and the mechanic couldn't figure it out. So they replaced the engine and the knock sensor fault was still present. only after replacing the ECU did the knock sensor go away. The car also ran worse with the original ecu and replacement engine.

[Off_Da_Wall]

Flyingferret said:

Coolant temperature sensor - my mum had a c3 with the 1.6 and it ran like a pig, wouldn’t idle or run very well. No fault code present for it either. It was defaulting to warm running settings and the ECU was throwing a fit. Cheap and handy to see if it fixes the fault.

I would have expected to possibly see that on the temp gauge on the dash but that shows to slowly warm up to operating temp as expected.

[stevemcs]

Cracked cam cover ? Vanos motor set correctly ?

[Megaflow]

Off_Da_Wall said:

Megaflow said:

It might not have an engine management light on, but does it have any fault codes? That is the first question.

I’d also be very sceptical about a constant knock sensor issues being a faulty ECU. ECU’s are generally very reliable, they have no moving parts and live inside the car or a waterproof enclosure. The sensors and wiring that feed them not so much.

Did the original engine get the knock sensor problem fixed before the timing chain jumped a tooth or during?

Shows no active codes and I can only get a P0420 when I take it on a long journey. The car had a knock sensor fault when I first bought the car thinking it was an easy fix replaced the sensor, checked the sensor connector, checked the ecu connector and checked the continuity from ecu connector to the sensor connector. The original engine would not run when timed correctly and the mechanic couldn't figure it out. So they replaced the engine and the knock sensor fault was still present. only after replacing the ECU did the knock sensor go away. The car also ran worse with the original ecu and replacement engine.

P0420 is basically just telling you it is not running correctly, which we know already.

So that tells us the problem is something the ECU cannot see.

Which makes this an interesting suggestion.

Off_Da_Wall said:

Flyingferret said:

Coolant temperature sensor - my mum had a c3 with the 1.6 and it ran like a pig, wouldn’t idle or run very well. No fault code present for it either. It was defaulting to warm running settings and the ECU was throwing a fit. Cheap and handy to see if it fixes the fault.

I would have expected to possibly see that on the temp gauge on the dash but that shows to slowly warm up to operating temp as expected.

I would not trust the gauge, they are basically little more than a posh warming light, if the engine even vaguely warms up, the gauge will rise, and it will then stay there until it hits a prescribed value and then it will go to the red.

I want to see on a scan tool that it is reaching actual operating temperature and coming into open loop fuel control.

[Off_Da_Wall]

stevemcs said:

Cracked cam cover ? Vanos motor set correctly ?

I'll add that to my list of things to check. I Haven't noticed any obvious cracks or damage to the cam cover. Any more info on the vanos motor? how can I check?

[E-bmw]

Off_Da_Wall said:

E-bmw said:

What year is it?

Check for un-metered air leaks which would cause the ECU to enrichen the mixture.

Most common in the intake pipework/rubbers from air filter to engine.

I assume you mean the 1.6 Turbocharged engine?

Decoke is commonly a possible helpful factor.

It's a 2010 and I was looking to possibly simplify the intake system because it's a stupid setup. It's the NA version so a little simpler I guess. The car uses a MAP sensor so only an inlet manifold leak would have an effect right?

My first thought would be don't do it, Suzuki spent lots of money designing it that way for several reasons. Just check that everything it as it should be.

Remove each bit & check it minutely and replace ensuring it is all seated correctly & sealed.

Yes, an inlet manifold leak would do it, do you have a decent scanner that can do live data to check the MAP sensor readings?

[itcaptainslow]

Off_Da_Wall said:

Flyingferret said:

Coolant temperature sensor - my mum had a c3 with the 1.6 and it ran like a pig, wouldn’t idle or run very well. No fault code present for it either. It was defaulting to warm running settings and the ECU was throwing a fit. Cheap and handy to see if it fixes the fault.

I would have expected to possibly see that on the temp gauge on the dash but that shows to slowly warm up to operating temp as expected.

Check the live data for the coolant temperature readings, you'll find them implausible if the CTS is faulty. It's a known issue with the early versions of this engine - we were forever replacing them when I was at a Citroen dealership. From memory there was an Info Rapid about the issue.

No codes are generated as the ECU doesn't "see" it as an issue, but it just fuels appropriately for the CTS returning readings of -30 degrees

[snotrag]

itcaptainslow said:

Off_Da_Wall said:

Flyingferret said:

Coolant temperature sensor - my mum had a c3 with the 1.6 and it ran like a pig, wouldn’t idle or run very well. No fault code present for it either. It was defaulting to warm running settings and the ECU was throwing a fit. Cheap and handy to see if it fixes the fault.

I would have expected to possibly see that on the temp gauge on the dash but that shows to slowly warm up to operating temp as expected.

Check the live data for the coolant temperature readings, you'll find them implausible if the CTS is faulty. It's a known issue with the early versions of this engine - we were forever replacing them when I was at a Citroen dealership. From memory there was an Info Rapid about the issue.

No codes are generated as the ECU doesn't "see" it as an issue, but it just fuels appropriately for the CTS returning readings of -30 degrees

100% - From your original description I immediately thought temperature sensor. Car thinks its cold when its not and is fuelling accordingly.

Important to note that the Temperature Readout on the dashboard on many modern cars is either:

A)synthesized/assumed, if it exists at all
or
B) Driven by a different temperature sensor than the actual ECU engine coolant temp sensor.


Check what the ECU is seeing by pulling the values from the diagnostics.

[Off_Da_Wall]

itcaptainslow said:

Check the live data for the coolant temperature readings, you'll find them implausible if the CTS is faulty. It's a known issue with the early versions of this engine - we were forever replacing them when I was at a Citroen dealership. From memory there was an Info Rapid about the issue.

No codes are generated as the ECU doesn't "see" it as an issue, but it just fuels appropriately for the CTS returning readings of -30 degrees

snotrag said:

100% - From your original description I immediately thought temperature sensor. Car thinks its cold when its not and is fuelling accordingly.

Important to note that the Temperature Readout on the dashboard on many modern cars is either:

A)synthesized/assumed, if it exists at all
or
B) Driven by a different temperature sensor than the actual ECU engine coolant temp sensor.


Check what the ECU is seeing by pulling the values from the diagnostics.

I've uploaded a couple of videos and pictures of some live data. - https://photos.app.goo.gl/u7FEWxT2ijVQLVDr5

The car wasn't completely cold when I started looking at the live data so the coolant temp was around 50 degrees after idling for a while it got up to 85 ish so the coolant sensor seems to be reading correctly.

The car is showing a few codes -

P2178
P0420

I believe these codes are present because the ECU is from a c4 Picasso, the same car the replacement engine came from I just had it unlocked.
UD128
P0565
P1536

The coolant temp reference value being -48 degrees looked a little strange but I don't know, is that normal?

I also see that the upstream sensor regulation status stayed in a closed loop and the downstream sensor regulation status was open loop.

[Megaflow]

Off_Da_Wall said:

I've uploaded a couple of videos and pictures of some live data. - https://photos.app.goo.gl/u7FEWxT2ijVQLVDr5

The car wasn't completely cold when I started looking at the live data so the coolant temp was around 50 degrees after idling for a while it got up to 85 ish so the coolant sensor seems to be reading correctly.

The car is showing a few codes -

P2178
P0420

I believe these codes are present because the ECU is from a c4 Picasso, the same car the replacement engine came from I just had it unlocked.
UD128
P0565
P1536

The coolant temp reference value being -48 degrees looked a little strange but I don't know, is that normal?

I also see that the upstream sensor regulation status stayed in a closed loop and the downstream sensor regulation status was open loop.

I am not sure where you live, you might be typing from the Artic Circle or Greenland, but I wager minus 48 degrees C is very much not normal...

[Off_Da_Wall]

Megaflow said:

I am not sure where you live, you might be typing from the Artic Circle or Greenland, but I wager minus 48 degrees C is very much not normal...

The question is where is the ECU getting the coolant temperature reference from🤔

[Megaflow]

Probably a second sensor, was quite common.

[GreenV8S]

Coolant temperature sensors are typically thermisters. These give a lower resistance as they get hotter. A very low temperature reading would indicate a high resistance, perhaps the result of an open circuit in the sensor or the wiring to it.